code: def _block_parallel_sync_behavior(
      strategy: Strategy, block: bool = True
  ) -> Generator[None, None, None]:
      """Blocks synchronization in :class:`~lightning.pytorch.strategies.parallel.ParallelStrategy`. This is useful for
      example when accumulating gradients to reduce communication when it is not needed.
  
      Args:
          strategy: the strategy instance to use.
          block: whether the context manager is enabled or not
  
      Returns:
          context manager with sync behaviour off
  
      """
      if isinstance(strategy, ParallelStrategy) and block:
          with strategy.block_backward_sync():
              yield None
      else:
          yield None
  
imports: import inspect
  from contextlib import contextmanager
  from typing import Any, Callable, ContextManager, Generator, Optional, Tuple, Type
  import torch
  import torch.distributed
  from torch import Tensor
  import lightning.pytorch
  from lightning.fabric.utilities.distributed import _distributed_is_initialized
  from lightning.fabric.utilities.imports import _TORCH_EQUAL_2_0, _TORCH_GREATER_EQUAL_1_13
  from lightning.fabric.utilities.warnings import PossibleUserWarning
  from lightning.pytorch.accelerators.xla import XLAAccelerator
  from lightning.pytorch.callbacks.timer import Timer
  from lightning.pytorch.loops import _Loop
  from lightning.pytorch.loops.fetchers import _DataFetcher, _DataLoaderIterDataFetcher, _PrefetchDataFetcher
  from lightning.pytorch.loops.progress import _BaseProgress
  from lightning.pytorch.strategies import FSDPStrategy
  from lightning.pytorch.strategies.parallel import ParallelStrategy
  from lightning.pytorch.strategies.strategy import Strategy
  from lightning.pytorch.trainer.states import RunningStage
  from lightning.pytorch.utilities.rank_zero import rank_zero_warn
  from lightning.pytorch.utilities.signature_utils import is_param_in_hook_signature
label_desc: Use image node_id 3 for calling a global function with example usage: _block_parallel_sync_behavior(strategy, block) without return types